It is known that drugs work most efficiently in the human body if they are delivered locally, e.g., to a specific tissue to be treated. When a drug is delivered systemically, tissues other than those being treated may be exposed to large quantities of that drug. This exposure presents a much greater chance for side effects. Targeting drug delivery to specific tissue often presents challenges, particularly if the targeted tissues are deep inside the body. In many cases, one or more doses of a drug or other agent can only be delivered to certain tissues with a specialized injection device.
One group of tissues which can be difficult to reach include the cochlea and other specific sub-cochlear locations in the inner ear. Therapeutic agents can be delivered to either the middle ear or the inner ear for the treatment of various diseases and conditions associated with inner ear tissue. Areas of the inner ear tissue structures where treatment can be beneficial include portions of the osseous labyrinth, such as the cochlea. However, the delivery of therapeutic agents to the inner ear in a controlled and effective manner is difficult due to the size and structure of the inner ear. The same is true of the tissue materials which separate the middle ear from the inner ear (e.g. the round window membrane). The inner ear tissues are of such sizes and locations that they are only readily accessible through invasive microsurgical procedures.
Access to the osseous labyrinth in the inner ear, including the cochlea, is typically achieved through a variety of structures of the middle-inner ear interface including, but not limited to, the round window membrane or the temporal bone. As known, the middle ear region includes the air-containing tissue zone between the tympanic membrane (e.g. the ear drum) and the inner ear. Currently, a variety of methods exist for delivering therapeutic agents to the middle ear and inner ear for treating inner ear diseases and conditions. These methods include drug injection through the tympanic membrane and surgically implanting drug loaded sponges and other drug releasing materials. Although conventional methods may ultimately result in the delivery of a therapeutic agent into the inner ear (e.g., by perfusion through the round window membrane), that delivery is generally not well controlled and the amount of the therapeutic agent that arrives within the inner ear is not precisely known.
Numerous other anatomical regions can be difficult to access without invasive surgical procedures. For example, it is often beneficial to treat cancer, allergy-related disorders and various auto-immune diseases by direct injection of drugs into a lymph node (e.g., treating allergies with immune suppressants or drugs that change the immune response from IgE to IgG). Many tumors can also be treated effectively with targeted delivery of various compounds. In many cases, however, a targeted lymph node, tumor or other anatomical region can only be located using specialized and time-consuming techniques such as radiological procedures, affinity techniques in which antibodies target cell surface antigens, or enzyme targeted pro-drug techniques. Supplying small amounts of a drug over an extended period to not-easily-accessible regions can pose practical problems. Each treatment may require a complicated, invasive and expensive medical procedure. Repeated surgical interventions over time are in most cases undesirable to the medical community and/or patients.
There are numerous other circumstances in which it may be desirable to deliver drugs or other agents in a tissue-specific manner on an intermittent or continuous basis. Examples include drug delivery to the brain for treatment of chronic pain, migraines, conditions of the auditory cortex, conditions of the inferior colliculus, and various neurological disorders.
In situations such as those described above, as well as in numerous other scenarios, conventional methods and systems do not deliver agents to a desired location in a controlled and efficient manner. As a result, the amount and frequency of agents introduced into an intended anatomical region cannot be effectively controlled.